Copper treated sulfurized fatty ester lubricant additives



CGPPER TREATED SULFURIZED FATTY ESTER LUBRICANT ADDITHVES Ford C. Teeter,Worth, Eugene F. Pisha, Oak Lawn, Leo P. Council, Harvey, and flharles A. Mazzoni, JL, Oriand Park, BL, assigncrs, by mesne assignments, to Sinclair Research Inc., New York, N.Y., a corporation of Delaware No Drawing. Filed Mar. 10, 1961, Ser. No. 94,702

g 6 Claims. (Cl. 252-464) This invention relatesto lubricant oils capable of use as cutting fluids. More particularly the invention relates to non-corrosive, sulfurized fatty esters as additives in cutting oils used in the machining of non-ferrous metals.

Many types of additives have been prepared and added to extreme pressure lubricant formulations for the purpose of augmenting film strength, lubricity and other desired characteristics. It has long been known that sulfur compounds, when added to lubricating oils, impart-certain properties to the mixtures which are of great value when these mixtures are used as lubricants for very heavy duty service such as is encountered in cutting and threading operations. The exact manner in which the sulfur compounds act to produce these results is not known with a degree of certainty.

It has been known that sulfurized products of unsaturated fatty acids and their derivatives, such as their esters, for instance sulfurized sperm oil, sulfurized rape seed oil, sulfurized cottonseed oil and sulfurized palm oil are effective extreme pressure agents. The sulfurized monohydric and dihydric alcohol esters of organic carboxylic' acids are known to be useful for blending with lubricants in preparing cutting oils.

These sulfur-containing compounds must be in a form which will be effective towards producing the desired improvement, yet they must be relatively non-corrosive towards metals, especially copper, under the conditions in which they are used. It has been found that lubricants containing these sulfurized esters exhibit undue metal corrosion tendencies, for instance the compositions are not satisfactory when evaluated by a copper corrosion test during which a test copper strip becomes covered with a heavy black sulfide type coating. It will be appreciated that the retention of the desirable effects of sulfur in a lubricant such-as high film strength is of little value unless the corrosive effects of the sulfur in the lubricant are overcome while at the same time retaining the advantageous characteristics of the lubricant. In the machining of non-ferrous metals it is highly important that the corrosiveness of the cutting oil be kept very low, Whereas the corrosiveness of lubricants used in internal combustion engines in not as critical as that of the cutting oils.

In accordance with the present invention it has been found that an improved lubricating oil composition can be prepared by incorporating in the oil a copper-treated sulfurized ester which exhibits desirable extreme pressure characteristics and yet unlike previously used materials, is not unduly corrosive to metal surfaces. The coppertreated sulfurized ester is present in the base lubricating oil in an amount sufficient to impart extreme pressure characteristics to the oil composition. The esterextreme pressure additive may be up to about 75 weight percent 01' more of the composition. In heavy duty metal cutting applications the copper-treated ester itself may be used but most often it is added to abase lubricating oil, for instance in amounts of more than about 5%, and is often about 40 to 70% of the composition. For instance, a'

composition containing 55% of copper-treated sulfurized sperm oil and 45% of mineral oil was used in the examples below. K

Our extreme pressure additive may be derived from fatty esters of mono-, di-, or trihydroxy alcohol. These liquid-air interface are rated; ASTM copper ratings are- 3,i32,l3 Patented May 5, 1864 alkanols frequently have up to about 20 carbon atoms. For instance the alcohol component of sperm oil esters consists essentially of monohydric alcohols containing l6 18 carbon atoms with little or none of the alcohols containing less than 14 or more than 20 carbon atoms. The esters of lower alkanols, say of 1 to 4 carbon atoms, are preferred in some instances. The ester is of an unsaturated fatty acid of about 12 to 22 carbon atoms, preferably about 14 to 18 carbon atoms. The mono-olefinic or acrylic acids are preferred and include, for example, behenic, erucic, and oleic acid esters. These acid esters may be used as mixtures, e.g. sperm oil, which may include saturated acid components. Among the esters that may be used are glyceryl trioleate and methyl oleate. Castor oil, lard oil, sperm oil, and other. fatty oils may also be used. In the practice of this invention the methyl ester of oleic acid and sperm oil are especially preferred.

The sulfurized esters employed in this invention are prepared by reacting the ester with elemental sulfur. O13 dinarily the sulfur is added in finely divided form which may be sifted in small increments into or otherwise added to a kettle containing the ester in amounts of about 1 to 20 parts of sulfur, preferably about 5 to 15 parts, to about to 99 parts of the ester, preferably about to parts. The mixture is well stirred and maintained at atemperature in the range of about 200 to 400 F., preferably about 300 to 350 F. for a period sufficient to complete the sulfurization. In obtaining the additive 7 ditive will not form a black coating. in the copper cor rosion test. Usually the mixture is heated at about 200 to 400 F. for at least about 15 minutes and preferably the time is about 1 to 6 or more hours while the temperature is about 315 to 365 F. Longer times do not seem harmful to the product but have not been found to be economically justified. After contact with the copper powder, the product is intimately contacted for at least about 1 hour to about 5 hours or more preferably about 1.5 to 3 hours, at an elevated temperature, usually about to 350 F., preferably about 225 to 275 F., with a gas which is essentially inert to the additive at these conditions, e.g., air, nitrogen, etc. The operation should not be conductedto a point of undue oxidation of the copper-treated product. Copper sulfide andexcess un-v reacted copper powder can be removed from the desired product by filtration. The amount of copper might be varied dependent upon particle size, i.e. less copper may be required with a powder of small particle size and vice .versa with a powder of larger particle size. The pre- Freshly polished strips of copper and brass are placed into individual 150 m1. open top beakers. The oil sample is poured into each beaker allowing the metal strip to be partially immersed. Two sets of metal are prepared in the above fashion; .One set is allowed to remain at room temperature (80 F.) while the other set is placed in an oven maintained at 150 F. and flooded with nitrogen at a rate of 5.5 cubic feet per hour. Duration of the test is 48 hours, after which time the strips are removed and washed with naphtha. Areas above and below the assigned to the copper strips while the brass specimens are evaluated on the basis of severity of stain.

TABLE I Effect of Air Treatment 2 Hrs. Air- No Airtreat treat at Composition:

Coastal Oil 100 SUS at 100 F 45. Additive (Copper-treated Suliurized Sperm Oil) 55. Copper, Top 1A. Copper, Bottom 3B fresh polish. Brass, Top slight stain no stain. Brass, Bottom "do D0. 150 F.:

Copper, Top 3B 1B2A. Copper, Bottom 3B lA-slight stain. Brass, Top Heavy stain very slight stain. Brass, Bottom -do no stain.

It will be noticed from Table I that failure to airtreat produces an additive considerably more corrosive to both brass and copper.

The base oil in our improved extreme pressure lubricant may comprise any petroleum or mineral lubricating oil fraction for instance, a solvent extracted or solvent refined oil obtained in accordance with conventional methods of solvent refining lubricating oils. Often lubricating oils have viscosities from about 50 to 1000 or more SUS at 100 F. The base oil may be derived from parafiinic, naphthenic, asphaltic or mixed base crudes, and if desired, a blend of solvent-treated Mid-Continent neutrals and Mid-Continent bright stock may be employed. Aside from the copper-treated additive the base oil is usually the essential balance of the composition. However, the compositions may also contain minor amounts of other additive agents such as pour depressors, viscosity index improvers, anti-oxidants, foam inhibitors, etc.

An illustrative example of the method of this invention which is to be considered non-limiting is as follows:

88 parts by weight of commercially pure methyl oleate prepared by esterifying methanol and oleic acid was heated to about 325 F. and 12 parts by weight of elemental sulfur were slowly added with stirring. After the sulfur had been added the reaction mixture was maintained at 325 F. for about 22 hours to give a material containing not more than about 20% sulfur. T about 100 parts of sulfurized methyl oleate, 5 parts of a finely divided metallic copper powder having a particle size of 200 mesh was added and the temperature raised to about 350 F. for about 2 hours. The copper sulfide and excess copper powders were removed from the desired product by filtration.

The data tabulated in Table II characterize methyl oleate, sulfurized methyl oleate and copper-treated sulfurized methyl oleate.

TABLE II Copper- Methyl Sulfurized Treated Oleate Methyl Snlfurized Oleate Methyl Oleate Specific Gravity 0.882 .977 0. 965 Flash, F 340 Fire, F 385 Viscosity at 100 F., SUS- 41. 5 154.8 127.7 0111, +5 +10 Carbon Residue, Percent 0.007 .77 0.61 Sultated Ash, Percent 0.003 .004 0.008 Iodine No 88. 2 Saponification N 188. 9 204.1 188. 2 Acid No. (D-974) 0.61 7. 59 7. 75 Free fatty Acid, Percent (as oleic)- 2 0. 2O 4. 67 4. 31 Sulfur, Percent 11.73 9.88

} Before sulfurization this was adjusted to 4.81 by addition of 2% oleic acid.

@fcfore sulfurization this was adjusted to 2.38 by addition of 2% oleic aci In the preparation of sulfurized sperm oil, the sperm oil can be reacted with suitable amounts of sulfur so that the final sulfurized product contains about 5 to 15% sulfur by treating this minture at a temperature of about 335 to 360 F. After all the sulfur has been added, the temperature is maintained at 345 F. tor about 6 hours. Finely divided metallic copper powder having a mesh size of about 200 is added amounting to 5% by weight based on the sulfurized sperm oil and the mixture is heated to 325 F. for 2 hours and then air treated for 2 hours at 250 F. The product is filtered recovering a sulfur-ized product containing about 12% sulfur.

The data tabulated in Table III characterize sulfurized sperm and copper-treated sulfurized sperm oil.

The effectiveness of the copper-treated sulfurized sperm oil prepared in accordance with this invention upon the corrosiveness of cutting oils useful in the machining of non-ferrous metals evaluated by the strip corrosion test and the results are reported in Table IV.

TABE IV Cutting Oil Stain Test [48 hours at room temperatures F.) and 150 F.]

Sulfurized Copper-Treated Additive Sperm Oil Sulturized Sperm Oil Composition, Wt. Percent:

Coastal Oil SUS at 100 F 45 45. 1additive 55 55. Copper, Top 1A. Copper, Bottom- Fresh polish. Brass, 'Iop No Stain. No Stain. Brass, Bottom Slight Stain Do. F.:

Copper, Top 3B lB-ZA. Copper, Bottom 3A 1A Slight Stain. Brass, Top Heavy stain, Very slight blue streaks. stain. Brass, Bottom d0 No stain.

It 18 to be noted that there is a definite reduction m copper strip activity when the s 'urized sperm oil is copper treated. The process of the present invention results in sulfurized ester products giving essentially no blackening in the copper corrosion [strip test where any significant blackening effect is undesirable and this result is obtained regardless of the degree of blackening caused by the untreated product.

We claim:

1. A composition which consists essentially of a mineral lubricating base oil having incorporated therein about 5 to 75% of an oil-soluble, copper-treated, sulfurized ester of an unsaturated fatty acid of about 12 to 22 carbon atoms and an alkanol of up to about 20 carbon atoms, said copper-treated sulfurized ester being prepared by the method of claim 4, and said ester being present in an amount suificient to inhibit said composition against corrosion to copper and brass.

2. The composition of claim 1 in which the coppertreated sulfurized ester is present in the range of about 5 to 70% by weight of the total lubricant composition.

5 6 3. The composition of 2 in which the ester su1 5. The method of claim 4 in which the temperature is ionized is sperm oil. about 315 to 365 F.

4. A method which consists'essentially of treating a sul- 6. The composition produced by the method of claim 4. furized ester of an unsaturated fatty acid of about 12 to a 22 carbon atoms and an alkanol of up to about 20 carbon 5 References Cited in the file Of this Patent atoms with about 0.5 to 10% of finely divided metallic UNITED STATES PATENTS copper havmg a pamcle slze not exceeding about 200 mesh, said treating being at a temperature of about 200 2,065,248 Smith 1935 to 400 F. for at least about 15 minutes and intimately 2,179,060 'P 1939 contacting the copper-treated product with an inept :gas 10 2,179,061 Smith 7, 1939 at an elevated temperature for at least about 1 hour. 2,349,820 7 FOX y 1944 

1. A COMPOSITION WHICH CONSISTS ESSENTIALLY OF A MINERAL LUBRICATING BASE OIL HAVING INCORPORATED THEREIN ABOUT 5 TO 75% OF AN OIL-SOLUBLE, COPPER-TREATED, SULFURIZED ESTER OF AN UNSATURATED FATTY ACID OF ABOUT 12 TO 22 CARBON ATOMS AND AN ALKANOL OF UP TO ABOUT 20 CARBONS ATOMS, SAID COPPER-TREATED SULFURIZED ESTER BEING PREPARED BY THE METHOD OF CLAIM 4, AND SAID ESTER BEING PRESENTED IN AN AMOUNT SUFFICIENT TO INHIBIT SAID COMPOSITION AGAINST CORROSION TO COPPER AND BRASS. 